1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly to a technique which is effectively applicable to a VA (Vertical Alignment) -type liquid crystal display device.
2. Description of the Related Art
Conventionally, as one of the liquid crystal display devices, a VA-type liquid crystal display device has been known. In the VA-type liquid crystal display device, when a voltage is an OFF level, that is, when a potential difference between pixel electrodes and counter electrodes (also referred to as common electrodes) is 0, liquid crystal molecules are oriented perpendicular to a planar surface of a substrate, while when the voltage assumes a maximum value, the liquid crystal molecules are oriented parallel to the planar surface of a substrate. Further, in the VA-type liquid crystal display device, a black display is performed when the voltage is turned off and a white display is performed when the voltage assumes the maximum value.
Further, in the VA-type liquid crystal display device, to enhance a viewing angle characteristic, an orientation division technique (multi-domain) of liquid crystal molecules is incorporated in many cases. The orientation division technique is a technique which divides a liquid crystal layer into small regions and changes the direction that the liquid crystal molecules is oriented in response to a voltage for every small region. That is, the liquid crystal molecules are inclined to the right in one region and the liquid crystal molecules are inclined to the left in another region. Accordingly, a light quantity of the whole screen is averaged thus largely suppressing a color change attributed to a viewing angle.
The principle of the orientation division technique is, for example, that when the voltage assumes an OFF level, the orientation of the liquid crystal molecules in a boundary between respective small regions is not arranged perpendicular to the planar surface of the substrate but is arranged in an inclined state with respect to a certain direction. As a specific method for controlling the direction that the liquid crystal molecules are inclined, for example, a method which applies the linear polarized light radiation treatment (see patent document 1, for example) and a method which forms orientation control projections (see patent document 2, for example) are named.
However, when the above-mentioned orientation division technique is applied to the liquid crystal display device, for example, in the region where the orientation control projections are present, when the voltage assumes an OFF level, the liquid crystal molecules are present in a state the liquid crystal molecules are inclined in the certain direction without being inclined perpendicular to the planar surface of the substrate. Accordingly, there arises a drawback that leaking of light is generated in the region where the orientation control projections are arranged thus lowering a black contrast.
To cope with such a drawback, in the above-mentioned patent document 1, leaking of light is lowered by shielding portions which have a plurality of tilting angles (inclination angles) from light with a light shielding pattern. Further, in the above-mentioned patent document 2, a light shielding film is formed at a position which corresponds to an orientation restricting means (orientation control projections).
[Patent document 1] JP-A-11-202338
[Patent document 2] JP-A-2005-173105